PHYSICAL PROPERTIES OF MATTER All three states of matter have certain properties that help distinguish between the states. Four of these properties are density, shape, compressibility, and thermal expansion.

A KINETIC MOLECULAR VIEW OF SOLIDS, LIQUIDS, AND GASES

DENSITY High density high – med density low density Density is equal to the mass of a sample divided by the volume of the same sample. High density high – med density low density

OTHER PHYSICAL PROPERTIES SHAPE The shape matter takes depends upon the physical state of the matter. COMPRESSIBILITY Compressibility is the change in volume of a sample of matter that results from a pressure change acting on the sample. THERMAL EXPANSION Thermal expansion is the change in volume of a sample of matter resulting from a change in the temperature of the sample.

Effusion and Diffusion Effusion is a process in which a gas escapes from a container through a small hole in the container. DIFFUSION Diffusion is a process that causes gases to spontaneously mix when they are brought together.

CHARACTERISTIC PROPERTIES OF THE THREE STATES OF MATTER

KINETIC ENERGY Kinetic energy is the energy a particle has as a result of being in motion. Kinetic energy (KE) is calculated using the equation: In this equation, m is the mass of a particle and v is its velocity.

POTENTIAL ENERGY & FORCES Potential energy is the energy a particle has as a result of being attracted to or repelled by other particles. COHESIVE FORCE A cohesive force is an attractive force between particles. It is associated with potential energy. DISRUPTIVE FORCE A disruptive force results from particle motion. It is associated with kinetic energy.

CHANGES IN STATE Changes in state are often accomplished by adding or removing heat from a substance. Changes in state caused by adding heat to a substance are classified as endothermic (heat in) processes. Changes in state caused by removing heat are classified as exothermic (heat out) processes. Add Heat Give off Heat

ENDOTHERMIC PROCESSES HEAT IS ADDED EVAPORATION OR VAPORIZATION Evaporation or vaporization is an endothermic process in which a liquid is changed to a gas. SUBLIMATION Sublimation is an endothermic process in which a solid is changed to a gas without first melting to a liquid. MELTING OR FUSION Melting or fusion is an endothermic process in which a solid is changed to a liquid.

EXOTHERMIC PROCESSES HEAT IS REMOVED CONDENSATION DEPOSITION FREEZING Condensation is an exothermic process in which a gas is changed to a liquid. DEPOSITION Deposition is an exothermic process in which a gas is changed into a solid. FREEZING Freezing is an exothermic process in which a liquid is changed into a solid.

VAPOR PRESSURE Vapor pressure is the pressure exerted by a vapor that is in equilibrium with its liquid. High vapor pressure = low boiling point

ENERGY AND THE STATES OF MATTER At 760 torr, constant heat is applied until a 1 g sample of ice at -20°C is converted to steam at 120°C. This is a five step process: (AB) heating ice to melting point, (BC) melting ice, (CD) heating liquid to boiling point, (DE) boiling water, and (EF) heating steam.

HEATS OF FUSION & VAPORIZATION SPECIFIC HEAT The specific heat of a substance is the amount of heat required to raise the temperature of exactly 1 g of a substance exactly 1°C. HEAT OF FUSION The heat of fusion of a substance is the amount of heat required to melt exactly 1g of a solid substance at constant temperature. HEAT OF VAPORIZATION The heat of vaporization of a substance is the amount of heat required to vaporize exactly 1g of a liquid substance at constant temperature.

GASES Intermolecular forces are minimal Move independent of each other High velocity – move in random motion Higher kinetic energy than liquids or solids Volume occupied is negligible compared to volume of container

PRESSURE PRESSURE Pressure is the force pushing on a unit area of surface on which the force acts. STANDARD ATMOSPHERE OF PRESSURE A pressure of one standard atmosphere is the pressure needed to support a 760-mm (76.0-cm) column of mercury in a barometer. ONE TORR OF PRESSURE One torr of pressure is the pressure needed to support a 1-mm column of mercury in a barometer. A pressure of 760 torr is equal to one standard atmosphere.

OFTEN-USED UNITS OF PRESSURE

TEMPERATURE The temperature of a gas sample is a measurement of the average kinetic energy of the gas molecules in the sample. The Kelvin temperature scale is used in all gas law calculations. ABSOLUTE ZERO A temperature of 0 K is called absolute zero. It is the temperature at which gas molecules have no kinetic energy because all motion stops. On the Celsius scale, absolute zero is equal to -273°C.

THE IDEAL GAS LAW PV= nRT R = The ideal gas law allows calculations to be done in which the amount of gas varies as well as the temperature, pressure, and volume. Mathematically, the ideal gas law is written as follows: PV= nRT R = P Pressure atm V Volume Liters n Number of moles moles T Temperature Kelvin R Universal gas constant

IDEAL GASES vs. REAL GASES No ideal gases actually exist. If they did exist, they would behave exactly as predicted by the gas laws at all temperatures and pressures. Real gases deviate from the behavior predicted by the gas laws, but under normally encountered temperatures and pressures, the deviations are small. Consequently, the gas laws can be used for real gases. Interparticle attractions make gases behave less ideally. The gas laws work best for gases made up of single atoms or nonpolar molecules.

AVOGADRO’S LAW Avogadro’s law states that equal volumes of gases measured at the same temperature and pressure contain equal numbers of molecules. STANDARD CONDITIONS STP = standard temperature and pressure 0°C (273 K) 1.00 atm MOLAR VOLUME AT STP 1 mole of any gas molecules has a volume of 22.4 L at STP.

IDEAL GAS LAW CALCULATIONS Example 1: A 2.50 mole sample of gas is confined in a 6.17 liter tank at a temperature of 28.0°C. What is the pressure of the gas in atm? Solution: The ideal gas equation is first solved for P: The known quantities are then substituted into the equation, making sure the units cancel properly to give units of atm in the answer:

IDEAL GAS LAW CALCULATIONS (continued) Example 2: A 4.00 g sample of gas is found to exert a pressure of 1.71 atm when confined in a 3.60 L container at a temperature of 27°C. What is the molecular weight of the gas in grams per mole? Solution: The molecular weight is equal to the sample mass in grams divided by the number of moles in the sample. Because the sample mass is known, the molecular weight can be determined by calculating the number of moles in the sample. The ideal gas equation is first solved for n: The known quantities are then substituted into the equation, making sure units cancel properly to give the units of mol for the answer.

IDEAL GAS LAW CALCULATIONS (continued) The units are seen to cancel properly to give the number of moles as the answer. The molecular weight is calculated by dividing the number of grams in the sample by the number of moles in the sample:

PRESSURE, TEMPERATURE, & VOLUME RELATIONSHIPS FOR GASES Mathematical equations relating the pressure, temperature, and volume of gases are called gas laws. All of the gas laws are named after the scientists who first discovered them.

VARIATION OF WATER BOILING POINT WITH CHANGE IN PRESSURE PV = nRT (Assuming V and n are equal) at high elevation  P decreases, T decreases Pressure cooker  P increases, T increases (cooks faster)

THE COMBINED GAS LAW Boyle's law and Charles's law can be combined to give the combined gas law that is written mathematically as follows: In this equation, P, V and T have the same meaning as before and k'' is another experimentally determined constant. The combined gas law can be expressed in another useful form where the subscript i refers to an initial set of conditions and the subscript f refers to a final set of conditions for the same gas sample.

GAS LAW EXAMPLE A gas sample has a volume of 2.50 liters when it is at a temperature of 30.0°C and a pressure of 1.80 atm. What volume in liters will the sample have if the pressure is increased to 3.00 atm, and the temperature is increased to 100°C? Solution: The problem can be solved: using the combined gas law. by identifying the initial and final conditions. making sure all like quantities are in the same units. expressing the temperatures in Kelvin. Thus, we see that the combined gas law must be solved for Vf.

GAS LAW EXAMPLE (continued) The result is: Substitution of appropriate values gives:

PARTIAL PRESSURE The partial pressure of an individual gas of a mixture is the pressure the gas would exert if it were alone in the container at the same temperature as the mixture as shown in the following illustration:

DALTON'S LAW OF PARTIAL PRESSURES According to Dalton's law, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the gases in the mixture. Zn(s) + NH4NO3(s) → N2(g) + 2 H2O(g)  + ZnO(s) P total = PN2 + PH2O